1. Field of the Invention
The present invention relates generally to interactive television systems, and more particularly, to the rapid acquisition, processing, storing and monitoring of schedule event information tables.
2. Summary of the Related Art
Interactive television systems are capable of displaying text and graphic images in addition to typical video program streams and provide a number of services and interactive applications to viewers. Generally, a broadcast service provider generates an interactive television signal for transmission to a viewer's television. The interactive television signal includes an interactive portion consisting of application code or system information, as well as an audio-video portion consisting of a television program. The broadcast service provide combines the audio-video and interactive portions into a single signal for transmission to a receiver connected to the viewer's television. The signal is generally compressed prior to transmission and transmitted through typical broadcast channels, such as cable television (CATV) lines or direct satellite transmission systems.
A set top box connected to the television controls the interactive functionality of the television. The set top box receives the signal transmitted by the broadcast service provider, separates the interactive portion from the audio-video portion, and decompresses the respective portions of the signal. The set top box uses the interactive information to execute an application while the audio-video information (after processing) is transmitted to the television, for example. The set top box may combine the audio-video information with interactive graphics or audio generated by the interactive application prior to transmitting the information to the television. The interactive graphics and audio may present additional information to the viewer or may prompt the viewer for input. The set top box may provide viewer input or other information to the broadcast service provider via a modem connection
The video, audio, and system information may be sent from a head end in various blocks of data via various transport mediums. For example, they may be sent from the head end via cable or satellite to the set top box. An example of the contents of such system information includes information regarding present or future events, services which the user of the set top box may access, and the current time and date. Examples of events include a television program (e.g., news, movie, sports), while an example of services includes a set of channels broadcast by the network (head end). Information on events is contained within an Event Information Table (EIT). This information is typically transferred from the head end to the set top box in EIT sections. These EIT sections are continuously re-broadcast by the head end due to the fact that the head end does not know when a set-top box is powered on.
Information on events scheduled to appear on various services may be requested by the viewer. However, due to bandwidth limitations the re-broadcast typically starts only every 20-30 seconds presenting an inherent delay in receipt of the EIT information. Hence, the time it takes for this information to be gathered, processed, and displayed on a television set may be significant due to the cycle time of the data delivered to the set top box. There is therefore, a need for a system and method for rapid acquisition time for receipt of EIT schedule event information, so that a viewer can quickly access the schedule information.
A head end might broadcast EIT-Schedule tables, which carry scheduling information for multiple days. A set top box may choose to either cache the schedule data (e.g. in memory) or to extract it from the broadcast stream in real time as the need arises. However, due to the fact that the size of the whole broadcast schedule data base may exceed available memory in the set top box, the set top box may choose to cache only part of the schedule database and acquire the remainder from the broadcast stream in real time as required.
A broadcast contains EIT schedule data as well as video, audio, network description and other data. The EIT schedule data is continuously repeated. The repeat time is called the cycle time. The EIT schedule broadcasts schedules for services in sequence, that is, service A, followed by service B, followed by service C, etc. A set top box will instruct a hardware filter to acquire schedule data for specific services. To prevent data overflow due to scheduling information arriving at a high bit rate and to reduce processing time, known systems set up hardware filters to acquire schedule data for a single service, for example service A. The hardware filter typically does not acquire any scheduling information for service B or C, etc.
Assuming that the set top box wants to acquire EIT scheduling information for service A, B and C, a typical EIT schedule engine would set up the hardware filter to acquit c the schedule data (section) for service A, then set up for the EIT section for service B and at last set up and acquire the EIT section for service C. The broadcast is repeated periodically, for example, every 30 seconds. Due to the fact that the hardware acquisition filter setup is in the same sequence as the broadcast schedule data, theoretically the schedule information could be acquired in a single cycle, if the acquisition and processing is fast enough to acquire a selected EIT schedule and set up the filter for the next service schedule prior to the next service schedule appearing on the broadcast.
Typical set top box processors, however, are not fast enough to acquire a selected service schedule, process it and set up the hardware filter before the next service schedule information section is presented in the broadcast stream. Moreover, if the EIT service schedule information sections are requested in reverse order, from which it is broadcast for example, requesting EIT sections for service C, service B, and then service A, the acquisition processor would have to set up the filter for service C, process the service C EIT section, wait another cycle until service B EIT section is rebroadcast, capture service B EIT and wait another cycle until service A EIT section is rebroadcast to capture the service A EIT. Thus, there is a need for an improved method and apparatus for rapidly acquiring EIT schedule information regardless or processor speed or the EIT event information broadcast sequence
The above is a brief description of some deficiencies in the prior art and advantages of the present invention. Other features, advantages, and embodiments of the invention will be apparent to those skilled in the art from the following description, drawings, and claims.